Question - (a) Show, giving a suitable diagram, how unpolarized light can be polarised by reflection.
(b) Two polaroids P1 and P2 are placed with their pass axes perpendicular to each other. Unpolarized light of intensity I0 is incident on P1. A third polaroid P3 is kept in between P1 and P2 such that its pass axis makes an angle of 60° with that of P1. Determine the intensity of light transmitted through P1, P2 and P3.
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Question - Using Rutherford model of the atom, derive the expression for the total energy of the electron in hydrogen atom. What is the significance of total negative energy possessed by the electron?
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Question - A parallel plate capacitor of capacitance C is charged to a potential V. It is then connected to another uncharged capacitor having the same capacitance. Find out the ratio of the energy stored in the combined system to that stored initially in the single capacitor.
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Question - Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area 2.5 x 10^-7 m^2 carrying a current of 2.7 A. Assume the density of conduction electrons to be 9 x 10^28 m^-3.
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Question - Using the concept of force between two infinitely long parallel current carrying conductors, define one ampere of current.
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Question - (a) Deduce an expression for the frequency of revolution of a charged particle in a magnetic field and show that it is independent of velocity or energy of the particle.
(b) Draw a schematic sketch of a cyclotron. Explain, giving the essential details of its construction, how it is used to accelerate the charged particles.
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Question - The graph shows variation of stopping potential V0 versus frequency of incident radiation ν for two photosensitive metals A and B. Which of the two metals has higher threshold frequency and why?
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Question - To which part of the electromagnetic spectrum does a wave of frequency 5 x 1011 Hz belong?
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Question - Why do the electric field lines never cross each other?
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Question - Write the functions of the following in communication systems:
(i) Receiver (ii) Demodulator
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Question - (a) A rod of length l is moved horizontally with a uniform velocity 'v' in a direction perpendicular to its length through a region in which a uniform magnetic field is acting vertically downward. Derive the expression for the emf induced across the ends of the rod.
(b) How does one understand this motional emf by invoking the Lorentz force acting on the free charge carriers of the conductor? Explain.
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Question - Show diagrammatically the behaviour of magnetic field lines in the presence of
(i) paramagnetic and
(ii) diamagnetic substances. How does one explain this distinguishing feature?
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Question - A heating element is marked 210 V, 630 W. Find the resistance of the element when connected to a 210 V dc source.
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